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01-21-2009, 02:04 AM   #1
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Matrix metering strange behavior...

Hello all!

Well, I had some time to kill last night between midnight an 2AM (or was it today ?), and so played with my k10's metering modes...

And here is something I noticed: although exposure values are displayed in real-time in the viewfinder in all modes (spot, CW and matrix) for a while after doing an half-press, they don't match what will be finally used by the k10 when using matrix metering!

That's right! Just move around your house (bulbs work quite well for this) and follow your exposure values. They move accordingly to what you point it at and what mode you're in, but in matrix mode, as soon as you do an half-press, they go to an entirely different realm!

My test was simple : frame a light bulb, note aperture/speed/sensibility, then half-press... The speed (was in Av at the time) repeatedly went from 1/100 to 1/1600!!!
And releasing the button sets the speed back to 1/100.

(It should be noted that the 1/100 value was found (and hold!) by the CW metering mode...)

Only positive thing I see with this is that you can check the exposure differences between CW and matrix in real-time...

01-21-2009, 02:59 AM   #2
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I am not sure I understand you.

Are you saying that you get drastically different exposures each time you do the half press ?

Also, make sure you have ISO set to a number, NOT auto, and that you have NOT set the camera to automatically adjust the exposure.

I think what you might be seeing is the ISO changing in auto mode.
01-21-2009, 06:44 AM   #3
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What I'm am saying is that the Aperture/Speed values change *drastically* when I half-press the shutter release. And no, I've not activated the auto-adjust feature.

In matrix mode, point a light bulb : it will read about 1/100, f/5.6, 100iso (with my 18-55 @ 55, hence the f/5.6).
Half-press : it jumps to 1/1600, f/5.6, 100iso.
Release : goes back to 1/100, f/5.6, 100iso...
You can repeat this as long as you wish...

Seems to me that the real-time value displayed while the shutter release IS NOT HALF-PRESSED is in fact the center-weighted value.

It's slightly less dramatic with more typical scenes : you'll see a 1/3Ev difference upon half-press.
01-21-2009, 06:55 AM   #4
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The only explanation I can think of for that behavior is that your camera is set to multi-zone AF, and that the custom setting for matrix metering to be biased for the AF point is activated.

I did not have time to test this yet, but I certainly don't recall such behaviour from my K10D. Mind you, I use a fixed AF point all the time.

01-21-2009, 07:20 AM   #5
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Nope, fixed AF point (center) here too...

I've just tried it again, and it's quite funny to alternate half-press/release and see the aperture/speed couple jiggle...
I've been one step further, and put the K10 in the green mode : pointing it to a light bulb, with given ISO value and AF point, you clearly see a huge difference (it went from 1/50-f/4.5 to 1/400-f/10 on half-press, then back on release!).
Select the CW metering mode, and the value stays at 1/50-f/4.5, half-press or not...
01-21-2009, 07:41 AM   #6
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interesting because i just tried this with my K10D and *istD and neither behaves as you report. at least in Av mode and P. I didn't try all modes or auto ISO etc, but for me metering is metering
01-21-2009, 07:51 AM   #7
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Really? Strange...

Just tried with disabling the "lock AE with AF point" feature, and it's still the same.
01-21-2009, 09:24 AM   #8
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QuoteOriginally posted by dlacouture Quote
Really? Strange...

Just tried with disabling the "lock AE with AF point" feature, and it's still the same.
I can understand it behaving the way you describe with the "lock AE with AF" function enabled.

With it disabled I dont understand why it would do this. I will have a play tonight and see what mine does.

You are keeping your eye to the viewfinder during all this arn't you ?

01-21-2009, 11:54 AM   #9
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QuoteOriginally posted by dlacouture Quote
Just move around your house (bulbs work quite well for this) and follow your exposure values. They move accordingly to what you point it at and what mode you're in, but in matrix mode, as soon as you do an half-press, they go to an entirely different realm!
My metering only works when I half-press.
How do you get the metering in the first place?
01-21-2009, 01:43 PM   #10
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Well my K10 does not behave like the OP's

When I half press to turn the meter on the shutter speed is displayed and doesn't change if i re-press the shutter half down. Changing metering mode to CW or spot will give a different shutter speed, but again the behaviour is normal whether I re-press the shutter half down or not.

If you have eliminated all the other suggestions in this post, I would say you have a faulty camera.
01-21-2009, 02:52 PM   #11
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I've never seen anything like this either. Which is the correct exposure?
01-21-2009, 04:00 PM   #12
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Check your custom settings to see how long the metering is set to be active. Default is 10 seconds, but it can be set to be either 30 or.... 3 (I think?)

My understanding is that this timer begins from the moment you release the half-held shutter button.
01-22-2009, 12:57 AM   #13
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The metering starts when you half press, not before.
You can only get the metering this way and pressing again changes nothing with regard to the metering, but only AF.

It might be helpful for dlacouture to do a reset of the custom settings (menu) and repeat.
Then he could explain again what exactly he is doing.
01-22-2009, 01:46 AM   #14
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OK, I've done some more tests...

This behavior only appears with the "Link Ae to AF Point" feature activated, and when there is a small bright source in the scene, near or at the center.

I've tried with AF on Auto, Select and Center, and it's the same behavior.

If you select a peripheral AF point and focus on the light source, you have no change at all...
But if you use center AF point (or, to a lesser extend, center left or center right), you'll see this behavior appear.

With standard scenes, it's not so dramatic, but sometimes you can still see a 1/3Ev variation...
01-22-2009, 02:11 AM   #15
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Blende8 : here are my settings...

- K10, 18-55 @ 55mm
- Subject : a light bulb, 2m aways, on a gray or dark background (used a ceiling light at work for the test today)
- Matrix metering (!)
- AF on Select, center point

Custom settings (those being relevant IMO):
- Program line = Depth
- Meter Operating time = 10s
- AE-L with AF locked = On
- Link AF point and AE = On
- Auto EV comp = Off
- AF button = cancel AF
- AF by press halfway = On
- Superimpose AF Area = On

Test done
- focus on the light bulb (should roughly fill the Spot brackets);
- release the shutter button (you can notice the metering stays active for the selected duration in "Meter Operating time");
- note the exposure values;
- Half-press (still with the light bulb in the center area) and note the exposure values;
- Release.

Another remark : by disabling "AE-L with AF locked" (or enabling it and pressing the AE-L button while half-pressing), if you move the view around, you'll notice that it's behaving a lot like a spot metering .
Which is fine by me, as if you point the camera straight at a small light source dead-center, then you surely want to properly expose this light source. But then, why does it not work this way when using peripheral focus points with "Link AF point and AE" enabled???

QuoteOriginally posted by blende8 Quote
The metering starts when you half press, not before.
You can only get the metering this way and pressing again changes nothing with regard to the metering, but only AF.
In fact, the metering is still active for a given time after releasing the button... And from what I saw, it's in fact the CW metering, and not the matrix metering, that is displayed during this "Meter Operating time" duration (when it's active but you don't maintain half-pressure).

Last edited by dlacouture; 01-22-2009 at 02:17 AM.
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